This article presents the theory of dual-mode gradient elution chromatography considering simultaneous spatial and temporal changes in the column temperature and mobile phase composition. In this technique, both solvent and temperature gradients propagate independently along the axial coordinate of the chromatographic column. The mathematical model of the underlying process contains nonlinear convection-dominated partial differential equations for mass, volume fraction of the solvent, and energy, coupled with algebraic or differential equations. The linear solvent strength retention model and the modified van’t Hoff retention behavior are utilized for expressing coefficients of Henry’s, nonlinearity, axial dispersion, and heat conductivity as functions of temperature and solvent composition. An extended high-resolution semidiscrete finite volume method is utilized for the numerical approximation of model equations. Numerous case studies have been conducted to assess the column performance for a variety of operating conditions. The benefits of dual-mode gradient elution, influencing the propagation speeds of concentration profiles, are thoroughly explored compared to that of isocratic operation. The results show a significant reduction in the retention time and a better performance of the column. Outcomes of this study will be useful for optimizing the model parameters and for further improving the process performance.

中文翻译：

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考虑柱温和溶剂组成同时变化的双模式梯度洗脱色谱的理论研究


本文介绍了考虑柱温和流动相组成同时空间和时间变化的双模式梯度洗脱色谱理论。在该技术中，溶剂梯度和温度梯度沿着色谱柱的轴坐标独立传播。基础过程的数学模型包含质量、溶剂体积分数和能量的非线性对流主导偏微分方程，以及代数方程或微分方程。线性溶剂强度保留模型和改进的范特霍夫保留行为用于将亨利系数、非线性、轴向色散和热导率表示为温度和溶剂组成的函数。采用扩展的高分辨率半离散有限体积法对模型方程进行数值逼近。已经进行了大量案例研究来评估各种操作条件下的色谱柱性能。与等度操作相比，双模式梯度洗脱的优点（影响浓度分布的传播速度）得到了彻底的探讨。结果表明，保留时间显着缩短，色谱柱性能更好。这项研究的结果将有助于优化模型参数和进一步提高过程性能。